Ground anchoring devices are used to secure above ground objects, such as premanufactured buildings, premanufactured homes, trailers, greenhouses and the like. Ground anchors protect and stabilize the buildings during adverse weather conditions, such as heavy winds, or ground tremors. For example, premanufactured buildings typically are mounted on a pair of parallel I-beams and ground anchors are positioned adjacent the side of the structure and tension straps extended at a slope upwardly from the around anchors to the I-beam. A ground anchor of this type is taught in U.S. Pat. No. 4,310,090.
As illustrated in FIG. 1 of the patent, ground anchors typically include an anchor shaft having a lower end for insertion into the ground and an upper end for positioning above the ground, at least one helically shaped auger blade fixedly attached to the lower end of the shaft and a winch mount fixedly attached to the upper end of the shaft. During installation, the anchor shaft is rotated in a direction in which the auger blades penetrate the ground and forcibly drive the anchor shaft in a downward direction. Often, the rotation of the anchor shaft is effected by a power driven installation driver such as a gas or electric motor. The installation driver is releasably coupled to the winch mount at the upper end of the anchor shaft.
The ground anchor is secured to the I-beams of the premanufactured building by a connecting member such as tie down strap, band, chain, belt or the like. Hereinafter, description of the prior art will refer to a tie down strap for securing a premanufactured building, however the description of prior art equally applies to other securing members and/or other ground objects. One end of the tie down strap is connected to the premanufactured building, such as with a U-shaped connector clip which attaches to an I-beam on which the premanufactured building is mounted. The other end of the tie down strap typically connects to a winch positioned in the winch mount at the upper end of the ground anchor. The tensioned tie down strap applies a downward sloped force to the premanufactured building, thereby resisting lateral and upward movement of the premanufactured building which may be caused by winds or ground tremors.
Ground anchors usually are installed after the premanufactured building has been placed at its permanent location. Because of the installation driver operating clearances, ground anchors usually are installed in a vertical position offset from the edge of the premanufactured building. Once the tie down strap has been connected between the ground anchor and the premanufactured building, the tie down strap is tightened to a desired tension. Because of both vertical and horizontal offset of the ground anchor from the I-beam of the premanufactured building, tension forces exerted by the tie down strap on the ground anchor have both vertical and horizontal force components. Vertical forces which tend to pull the ground anchor upwardly are resisted by the forces exerted by the auger blades embedded in the soil.
However, the prior art ground anchor alone can not effectively resist the lateral forces exerted by the tensioned tie down strap. As the ground anchor is driven into the ground by the installation driver, the auger blades engage and cut into the soil to draw the anchor shaft down into the ground. As the auger blades cut through the soil, a hole is formed and is filled with a column of disturbed soil. This disturbed soil, which is loose and easily moved about, can not provide significant resistance to lateral forces exerted on the anchor shaft. The demarcation between the column of disturbed soil and the undisturbed soil is the anchor hole side wall. As the tie down strap is tightened, the top of the anchor shaft is pulled sideways through the loose dirt until the shaft engages a solid structure, such as the anchor hole side wall or some additional restraining element.
Often, this additional restraining element may be a stabilizer plate pounded down into the ground adjacent the anchor shaft in a position between the anchor shaft and the premanufactured building. The stabilizer plate typically is made of a single steel plate, or of a similar material, approximately one foot wide having a bottom portion sufficiently deep so that the bottom portion can be firmly embedded in the soil. The ground anchor is first rotated and drawn partially into the ground by the auger blades. Next, the stabilizer plate, which is not a part of the anchor, is placed in abutment with the anchor shaft and pounded into the ground. Then, rotation of the anchor is resumed until the winch mount at the upper end of the shaft rests near the upper edge of the stabilizer plate.
After installation of the ground anchor and the stabilizer plate, a tie down strap is attached to the winch mount and the premanufactured building. The tie down strap is winched tight to a desired tension. As the tie down strap is tensioned the anchor shaft bends or flexes as the anchor shaft upper end is pulled laterally by the tension strap toward the stabilizer plate. Once the ground anchor shaft engages the stabilizer plate, lateral movement of the top end of the anchor shaft is stopped and the tie down strap can be tightened to the desired tension. The stabilizer plate provides a much broader bearing surface against the ground, so that the lateral forces applied by the ground anchor to the stabilizer plate are spread over a much larger cross-sectional area. This provides the ground anchor with substantially increased lateral strength.
Several problems and difficulties are encountered with the prior art as described. Installation of the stabilizer plate increases the installation time and adds cost. The stabilizer plate is manually driven into the ground by the installer, usually by striking or pounding the top portion of the stabilizer plate with a sledge hammer or other type of impact tool. If the ground anchor is initially installed too close to the trailer, pounding the stabilizer plate into the ground may be extremely difficult, if not impossible, because the installer would lack sufficient clearance from the premanufactured building for an effective and efficient swing of the sledge hammer. As is well known by one in the art, pounding objects into the ground with a sledge hammer presents a safety risk to the installer. Also, the premanufactured building may be accidentally hit by the sledge hammer, causing damage to the premanufactured building. Thus, a heretofore unaddressed need exists in the industry for a way to provide for an improved ground anchor with a stabilizing device which installs easily, quickly and safely.
Furthermore, to provide sufficient stabilizing support to the anchor shaft, the stabilizer plate should be sufficiently wide to be embedded firmly in the undisturbed soil outside of the hole made by the auger blades when the anchor shaft was rotated down into the ground. Prior art stabilizer plates typically are approximately one foot wide. Also, the stabilizer plate should be pounded into the ground perpendicular to the ground surface and centered under the tie down strap. However, the stabilizer plate is likely to shift in the ground with each impact of the sledge hammer and will most probably end up in a final position which only approximates the desired perpendicular position. Additionally, other objects around the premanufactured building, such as sidewalks, trees or decorative landscaping, may require a narrow stabilizer plate or may prevent installation of the stabilizer plate in a preferred position. One experienced in the art will realize that if the stabilizer plate is not perpendicular to the surface of the ground, or if the stabilizer plate is not normal to the vertical plane of the tensioned tie down strap, then the resistive force exerted by the stabilizer plate is not maximized because the effective cross-sectional area of the stabilizer plate is not maximized. Thus, a heretofore unaddressed need also exists in the industry for a way to provide for a ground anchor stabilizing device which effectively opposes the horizontal forces created by the tensioned tie down strap independent of the location of the ground anchor, the position of the stabilizer plate and/or the position of the tie down strap.
In the absence of a stabilizer plate or other restraining element, bending or flexing the upper portion of the anchor shaft toward the premanufactured building causes the anchor to depend mostly on its auger blades to resist pulling out from the ground, instead of using both the auger blades and the stabilizer plate to resist the pulling forces. The degree of anchor shaft bending or flexing depends upon the soil conditions, less bending with hard soils and more bending with soft soils. If a stabilizer plate is employed, there may be less bending of the anchor shaft as the anchor shaft is pulled into engagement with the stabilizer plate, depending upon the positioning of the stabilizer plate. However, a heretofore unaddressed need exists in the industry for a way to provide for a ground anchor stabilizing device which substantially reduces the bending or flexing of the upper end of the anchor shaft.
In the absence of a stabilizer plate or other restraining element, the top portion of the side wall of the hole made in the ground by the auger blades of the ground anchor when installed in the ground would likely be damaged when the anchor shaft engages the side wall as the tie down strap is tightened. If the side wall is not permanently stabilized after installation of the ground anchor, the tie down strap will eventually loosen as the side wall is further damaged by the constant force exerted by the anchor shaft or by subsequent erosion of the soil. Alternatively, the side wall of the anchor hole may be damaged when the stabilizer plate is driven into the ground. The strap would loosen if there is any subsequent settling or movement of the stabilizer plate. Thus, a heretofore unaddressed need exists in the industry for a way to provide for an improved ground anchor stabilizing device which provides adequate anchor support in soft or hard soil conditions, and does not damage the soil around the top end of the anchor hole side wall.